fill or drain near transducer

Will water from the fill or drain interfere with the transducer? It's long type, 4 or 6 inches.

It can.

I don't see why it would. The transducer face should be just below the bottom of the hull and the inlet/outlet are above the bottom. Neither should cause enough turbulence to effect the readings. At the very worst, there might be a sight amount of noise that would show as surface clutter.

Some ducers are much more sensitive than others. OP didn't specify what ducer and what head unit is in question. We've had issues before with certain ducers and head units picking up even small amounts of turbulence--hence why I said "it can".

Myself-I'm using an OLD school Humminbird, forget the model, but it's about 30 years old and does what "I" need it to do (I don't ask much of it), and it's not that sensitive to turbulence and/or air bubbles. BUT....at one point I had a bigger boat with an HDS-7(3d) on it and it would pick up almost everything out of the ordinary in it's best placement. Worst placement it didn't pick up anything and showed a bunch of jibberish on the screen. DI and SI units seem to be real sensitive too-which is what we had the most problem with (Lowrance E7 Ti). On the Lowrance, even the EMI from the trolling motor wires being tied together with the ducer cable would mess with it if that tells you anything. Had to isolate the ducer cabling from everything else-which seemed to work pretty good.

It's a Garmin Striker 7sv. It says to mount it to the right of the prop if possible, a foot away. At the rate my boat is going it may be ancient by the time I use it.

I have a Hummingbird DI transducer. Hummingbird says turbulence can cause unwanted noise. They also say that if a boat is left out of the water a long time small air bubbles can cling to the transducer and cause noise. If transducers are that sensitive then I would guess* if boat is sitting still and the drain or fill creates bubbles or turbulence then yes it could cause interference. Possibly could be the same even at slow (trolling) speeds. Moving faster than idle, I would guess not, but who knows.

*emphasis on "guess" haha